Is it published on a bicycle map?
Do you calculate an average using distance and elevation on topo maps?
Do you calculate it using a cyclocomputer and a GPS?
Do you look at the hill and guess? (my current method)
Is there some other device, bike mounted or handheld, for finding the slope of a hill?

I have been wanting to find the grade some of the hills I ride. I have something I use for finding the slope of ramps and roofs on buildings, but I don't want to carry it around, stop, get off the bike mid-climb or mid-descent and measure.

i dont know this to be a fact but if you have a cyclocomputer with altimiter abilities you might be able use the total distence traveled combined with the vertical distence traveled to make a triangle and then calculate the angle.

just a guess, im sure there are much better ways.

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Rise over run... calculate the rise of a hill in ft (or meters, whatever) and divide by it's length. For instance, if you use an altimiter and measure a 100 ft altitude gain over 1000 feet, it's a 10% avg grade. In practice, once you know what 10% looks and feels like, you can subjectively gauge what 5% or 15% are. For reference, I've heard that typical freeway on/off ramps (to an overpass) are graded at 4%...not sure that's true or consistent.

Ask that guy in your cycling club who talks about all the grades of all the hills and divide his answer by 2.

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If it's big enough you can go here http://www.topozone.com/ and calculate rise over run and get fairly close on an average grade. It's really tough to get accurate grades at different points without equipment or plotting the route in topographic software (which isn't always accurate either).

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i dont know this to be a fact but if you have a cyclocomputer with altimiter abilities you might be able use the total distence traveled combined with the vertical distence traveled to make a triangle and then calculate the angle.

Sort of. From there you'd need pythagorus to figure out the "run" part and then you can calculate the grade.

Turn out something like:

gradient = vertical/(Sqrroot(distance^2 - vertical^2))

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For the major climbs, I take a "profile" picture of the grade at one point, using something that sticks straight up as a guide. I then figure out the grade using bitmap, and the rise/run thing. Obviously this only works on the climbs that have a fairly steady climb. For others, I have some topo maps of the area, but they only go down to 100ft isolines so it's hard to be 100% accurate with those. Some others, I just eyeball and use my past experience to guesstimate.

Is it published on a bicycle map?
Do you calculate an average using distance and elevation on topo maps?
Do you calculate it using a cyclocomputer and a GPS?
Do you look at the hill and guess? (my current method)
Is there some other device, bike mounted or handheld, for finding the slope of a hill?

I have been wanting to find the grade some of the hills I ride. I have something I use for finding the slope of ramps and roofs on buildings, but I don't want to carry it around, stop, get off the bike mid-climb or mid-descent and measure.

How do you find the % grade.

I'm not a mathematician, so don't recall the elegant language for explaining this, but here is my attempt:

Degree of slope is often confused with percent of slope. Degree of slope is the measure of the number of degrees in the included angle, measured from level to the top of the hill (90 degrees is the angle when looking straight up, 0 degrees is dead level, 45 degrees is 1 foot up over 1 foot horizontal, or 100% slope). It is not at all uncommon to hear someone say something like "I was on a section of road that was 15 degrees up," which is 26.8 percent slope. Very Steep.

For personal purposes, I take my data from one of a number of mapping programs that give elevation data. These days, I also use readings off a GPS unit (ETrex Legend). Elevation data taken from USGS maps is often not accurate enough to give a good read for specific hill grades- it's very hard to get a good starting and ending elevation from a map that only gives elevation in 20' intervals, as are USGA maps, typically. If your hill is short, accuracy sucks, as your potential for elevation error (as much as 40' off) has a more profound effect on your computation than when the error is incorporated into a big distance. So, accuracy of percent slope estimated from USGA gets better as distance increases.

A clinometer (a hand held device, often integrated into a hand compass, but also available as a stand-alone unit) measures slope, and if used properly (measure from eye height to eye height- not eye height to ground) can be reasonable accurate (for bicylists), and is often used by foresters who need reliable estiation of grade values.

Guessing is rarely accurate for most folks- 2% on pavement looks flat to many. On the other extreme, people often guess a steep section of road as being steeper than it is (a BF poster from a while back was guessing that the slope they were riding up was 30 degrees, or 33% slope- This will never happen on any engineered, paved road in the US, except on the inside of very tight hairpin turns- this is an impossibly steep grade for a road). If you're really good at estimation (because you're a surveyor, civil engineer, landscape architect, or someone else who deals with grade change on a regular basis) you've probably developed a good sense of grade, but this is a skill that takes considerable practice to develop.

While I'm enough of a geek to have set up an Excel spreadsheet to calculate these things, just dividing the rise by the distance ridden (the hypotenuse) is pretty close to dividing the rise by the calculated horizontal run for most ridable grades.

Not to be geometrically anal about it, but does measuring road distance give you an accurate rise-over-run? Specifically, the run part? If your hill forms a right triangle, then the short leg of the triangle is your rise, that's straightforward; but in a true slope calculation, the "run" is the bottom leg of the triangle, not the sloped leg (hypotenuse), which is what's being measured if you rely on your cyclocomputer's mileage. The difference is probably trivial, but might cause you to slightly underestimate the slope (too long a run for a given rise). Any math weenies have insight into this?

Not to be geometrically anal about it, but does measuring road distance give you an accurate rise-over-run? Specifically, the run part? If your hill forms a right triangle, then the short leg of the triangle is your rise, that's straightforward; but in a true slope calculation, the "run" is the bottom leg of the triangle, not the sloped leg (hypotenuse), which is what's being measured if you rely on your cyclocomputer's mileage. The difference is probably trivial, but might cause you to slightly underestimate the slope (too long a run for a given rise). Any math weenies have insight into this?

If the grade is less than 20% or so, the difference between horizontal and hypotenuse is probably significantly less than your measurement error. For very short steep hills, you can convert using trigonometry or pythagoras.